Allochronic isolation on a latitudinal gradient in the polyphagous moth Hyphantria cunea

Allochronic speciation, where reproductive isolation between populations of a species is facilitated by a difference in reproductive timing, depends on the existence of seasonality. Seasonality is strongly driven by latitude, so there may be a relationship between latitude and divergence among populations separated by life history timing. Here we explore the relationship between allochronic speciation and latitude using Hyphantria cunea (the fall webworm), a Lepidopteran defoliator with red and black colour morphs that may be undergoing an incipient allochronic speciation. We annotated >9000 community science observations of fall webworm to model colour morph phenology and differences in phenotype across North America. We also examined the physiology of two sympatric populations to determine differences in diapause intensity. We found the fall webworm is multivoltine with differing numbers of generations between colour morphs at lower latitudes, and univoltine at latitudes higher than 41°. This shift to univoltism correlated with a decline in morphological differentiation. This shows that conditions at lower latitudes facilitate greater divergence in an incipient allochronic speciation potentially due to longer reproductive seasons allowing for greater mismatches in generations. Our results demonstrate how latitude affects allochronic speciation, and how sympatric speciation along latitudinal gradients contributes to trends in global biodiversity.

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Effects of Autumn Warming on Energy Consumption of Diapausing Fall Webworm (Lepidoptera: Arctiidae) Pupae

Journal of Insect Science ◽

10.1093/jisesa/ieab021 ◽

2021 ◽

Vol 21 (2) ◽

Author(s):

Lvquan Zhao ◽

Wei Wang

Keyword(s):

Energy Consumption ◽

The Body ◽

Latitudinal Gradients ◽

Liaoning Province ◽

Hyphantria Cunea ◽

Spreading Process ◽

Temperature Changes ◽

Protein Consumption ◽

Nanjing City ◽

Fall Webworm

Abstract Since its invasion into China in 1979, the fall webworm, Hyphantria cunea Drury, has spread from Dandong city (about 40°N) in Liaoning Province to Nanjing city (about 32°N) in Jiangsu Province, and to other areas. Owing to geographic and latitudinal gradients in temperature, H. cunea will encounter temperature changes during the spreading process. In this study, we verified the hypothesis that autumn warming accelerates the energy consumption of H. cunea diapause pupae. We found that, after autumn warming, the body size and mass of diapause pupae decreased significantly and raised constant temperature accelerated carbohydrate and protein consumption in female pupae, while fluctuating temperature changes had a more pronounced effect on carbohydrate and protein consumption in male pupae. Contrary to expectations, the lipid content of diapause pupae did not decrease after autumn warming, and even increased significantly. We conclude that warming in autumn accelerates energy consumption by diapause pupae, and the autumn energy consumption of diapause pupae is dominated by carbohydrates, supplemented by protein when carbohydrates are overconsumed, while lipid use is dominated by anabolic metabolism during autumn.

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Plasticity of nutrient accumulation patterns in diapausing fall webworm pupae

Bulletin of Entomological Research ◽

10.1017/s0007485321000201 ◽

2021 ◽

pp. 1-8

Author(s):

Lvquan Zhao ◽

Wei Wang ◽

Ying Qiu ◽

Alex S. Torson

Keyword(s):

The Body ◽

Diapause Induction ◽

Energy Reserve ◽

Short Photoperiod ◽

Induction Phase ◽

Energy Reserves ◽

Hyphantria Cunea ◽

Survival And Reproduction ◽

Fall Webworm ◽

Diapause Incidence

Abstract The accumulation of nutrients during diapause preparation is crucial because any lack of nutrition will reduce the likelihood of insects completing diapause, thereby decreasing their chances of survival and reproduction. The fall webworm, Hyphantria cunea, diapause as overwintering pupae and their diapause incidence and diapause intensity are regulated by the photoperiod. In this study, we test the hypothesis that photoperiod influences energy reserve accumulation during diapause preparation in fall webworm. We found that the body size and mass, lipid and carbohydrate content of pupae with a short photoperiod during the diapause induction phase were significantly greater than those of pupae with a relatively short photoperiod, and the efficiency of converting digested food and ingested food into body matter was greater in the short-photoperiod diapause-destined larvae than the relatively short-photoperiod diapause-destined larvae. We also observed higher lipase and amylase activities in short-photoperiod diapause-destined larvae relative to the counterparts. However, no obvious difference was found in protein and protease in the pupae with a short photoperiod during the diapause induction phase and short-photoperiod diapause-destined larvae compared with the counterparts. Therefore, we conclude that the energy reserve patterns of diapausing fall webworm pupae are plastic and that short-photoperiod diapause-destined larvae increase their energy reserves by improving their feeding efficiency and increase their lipid and carbohydrate stores by increasing the lipase and amylase activities in the midgut.

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